Optical waveguide having diffraction grating area and method of fabricating the same

ABSTRACT

The present invention is to provide a method for identifying an optical line easily and accurately regardless of the optical line length. A plurality of reflecting parts is placed on the optical line, and a combination of relative positions of the reflecting parts is changed for every optical line to form an identification code, and the relative positions of the reflecting parts are detected based on reflected lights when a detecting light is inputted to the optical line, so that the optical line is identified based on a result. Concretely, when the detecting light is inputted to one end of the optical line, the light is reflected at the plurality of the reflecting parts which form the identification code and comes back the input end. A combination of the relative positions etc. of the reflecting parts is changed for every optical line. To detect the relative positions of the reflecting parts which form the identification code, either the optical path difference of the reflected lights from the reflecting parts is measured or the time difference between the reflected lights come back from the reflecting parts is measured. Then, based on the result, the optical line can be identified.

This is a division of application Ser. No. 08/170,297, filed Dec. 30,1993 now U.S. Pat. No. 5,506,674.

TECHNICAL FIELD

This invention relates to a method for identifying an optical line atone end thereof which is used in optical communication system.

BACKGROUND ART

A method for identifying an optical line by varying a refractive indexof an optical line core in part, and detecting a position of the variedrefractive index part at one end of the optical line using the OTDRmethod has been known ("Remote Fiber Discrimination Method for anOptical Transmission Line Database", 1991, DENSI JYOUHOU TSUSIN GAKKAISHUKI TAIKAI, Reference B-591).

However, according to this method, an identification code composed ofthe varied refractive index parts on the optical line extends overhundreds meters. For instance, in an example of the reference describedabove, to record a 8 bits identification code on the optical linerequires a 50 m for a bit and a total of 400 m. Accordingly, it isdifficult to apply the identification code to a short optical line.Recording the identification code extending over hundreds meters on theoptical line has to be done during a manufacturing process of theoptical line, which is not practical.

DISCLOSURE OF THE INVENTION

An object of this invention is to provide a method for identifying anoptical line easily and accurately regardless of the optical linelength.

In order to achieve the object, a first method of the present inventioncomprises the steps of:

forming a plurality of the reflecting parts on each optical line as anidentification code, the each optical line having a specific combinationof relative positions of the reflecting parts;

detecting the relative positions of the reflecting parts based onreflected lights when a detecting light is inputted to the optical line;and

identifying the optical line based on a result of the detecting step.

When the detecting light is inputted to one end of the optical line, thelight is reflected at the plurality of the reflecting parts, and comesback to the input end. A combination of the relative positions of thereflecting parts is changed for every optical line. To detect therelative positions of the reflecting parts forming an identificationcode, either the optical path difference of the reflected lights ismeasured with the interferometer or the time difference between thereflected lights coming back from the reflecting parts is measured, sothat the optical line can be identified based on the result.

A second method of the present invention comprises the steps of:

forming a plurality of the reflecting parts on each optical line as anidentification code, the each reflecting part reflecting a light havinga specific wavelength, and the each optical line having a specificcombination of the specific reflecting wavelengths;

detecting wavelengths of the reflected lights when a detecting light isinputted to optical line; and

identifying the optical line based on a result of the detecting step.

When the detecting light is inputted to one end of the optical line, thelight is reflected at the reflecting parts which form an identificationcode and comes back to the input end. As a combination of thewavelengths of the reflected lights at the reflecting parts is changedfor every optical line, the wavelengths of the reflected lights aremeasured, so that the optical line can be identified based on theresult.

A third method of the present invention comprises the steps of:

forming a plurality of the reflecting parts on each optical line as anidentification code, the each reflecting part reflecting a light havinga specific wavelength, and the each optical line having a specificcombination of the specific reflecting wavelengths and reflectances;

detecting wavelengths and reflectances of the reflected lights when adetecting light is inputted to optical line; and

identifying the optical line based on a result of the detecting step.

When the detecting light is inputted to one end of the optical line, thelight is reflected at the reflecting parts which form an identificationcode and comes back to the input end. As a combination of thewavelengths and reflectances of the reflecting parts is changed forevery optical line, the wavelengths and the light intensities of thereflected lights are measured, and based on the result, the optical linecan be identified.

A fourth method of the present invention comprises the steps of:

forming a reflecting part on each optical line as an identificationcode, the reflecting part on the each optical line having a specificreflectance characteristic depending on a wavelength;

detecting reflected light spectra coming back from reflecting part whena detecting light is inputted to the optical line; and

identifying the optical line based on a result of the detecting step.

When the detecting light is inputted to one end of the optical line, thelight is reflected at the reflecting parts which form an identificationcode and comes back to the input end. As a reflectance characteristicdepending on a wavelength of the reflecting parts is changed for everyoptical line, the reflected light spectra are measured, and based on theresult, the optical line can be identified.

A fifth method of the present invention comprises the steps of:

forming a plurality of the reflecting parts on each optical line as anidentification code, the each reflecting part reflecting a light havinga specific wavelength, and the each optical line having a specificcombination of the specific reflecting wavelengths and relativepositions of the reflecting parts;

detecting wavelengths and relative positions of the reflected lightswhen a detecting light is inputted to optical line; and

identifying the optical line based on a result of the detecting step.

When the detecting light is inputted to one end of the optical line, thelight is reflected at the reflecting parts which form an identificationcode and comes back to the input end. As a combination of the specificwavelengths and relative positions of the reflecting parts is changedfor every optical line, the wavelengths and arrival times of thereflected lights from the identification code are measured, and based onthe result, the optical line can be identified.

A sixth method of the present invention comprises the steps of:

forming a plurality of bending loss parts on each optical line as anidentification code, the each optical line has a specific combination ofrelative positions of the plurality;

detecting the relative positions of the plurality based on abackscattering when a detecting light is inputted to the optical line;and

identifying the optical line based on a result of the detecting step.

When the detecting light is inputted to one end of the optical line, thelight is reflected at the reflecting parts which form an identificationcode and comes back to the input end. As a combination of the bendingloss parts is changed for every optical line, a time difference betweenthe backscattering lights coming back from the identification code ismeasured to detect the relative positions of the bending loss parts, andbased on the result, the optical line can be identified.

A seventh method of the present invention comprises the steps of:

forming reflecting parts on the core optical lines of the multicoreoptical line selectively as an identification code,

the each multicore optical line having a specific combination ofexistences of the reflecting parts and characteristics of reflections;

detecting reflected lights when detecting lights are inputted to themulticore optical line;

identifying the multicore optical line based on a result of thedetecting step.

When the detecting light is inputted to one end of the multicore opticalline, the light is reflected at the reflecting parts which form anidentification code and comes back to the input end. As a combination ofthe existence of the reflecting parts on every core optical fiber ischanged for every multicore optical line, the existence of the reflectedlights on the core optical fibers is measured, so that the optical linecan be identified.

In the first to seventh method, the identification code is placeddirectly on the optical line, but instead of this, it is possible toapply a branch optical line having the identification code to theoptical line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a control system of optical lines facilitywhich is applied to a method for identifying an optical line of thisinvention.

FIG. 2 is a block diagram of an inner structure of a code reading deviceand its peripheral devices according to an embodiment of the firstinvention.

FIG. 3 shows an example of an identification code.

FIG. 4A and FIG. 4B show a method for converting an interferogram to abinary code information.

FIG. 5 shows a branch optical line on which an identification code isformed.

FIG. 6 is a block diagram of another structure of a code reading device.

FIG. 7 is a graph of a detecting result.

FIG. 8 is a block diagram of an inner structure of a code reading deviceand its peripheral devices according to embodiments of the second,third, and fourth invention.

FIG. 9A shows an example of an identification code according to theembodiments of the second, third, and fifth invention.

FIG. 9B shows an example of an identification code according to theembodiments of the second, third, and fifth invention.

FIG. 10A is a graphic representation which shows a method for convertinga reflected light to a binary code information according to theembodiments of the second and fifth invention.

FIG. 10B is a table which shows a method for converting a reflectedlight to a binary code information according to the embodiments of thesecond and fifth invention.

FIG. 11 shows a branch optical line on which an information code isformed.

FIG. 12 is a block diagram of a structure of another code reading deviceaccording to the embodiments of the second, third and fourth invention.

FIG. 13 is a perspective view of a structure of another reflecting partaccording to the embodiments of the second, third, fourth, and fifthinvention.

FIG. 14 is a perspective view of a structure of another reflecting partaccording to the embodiments of the second, third, fourth, and fifthinvention.

FIG. 15A is a graphic representation which shows a method for convertinga reflected light spectrum to a quaternary code information according tothe embodiment of the third invention.

FIG. 15B is a table which shows a method for converting a reflectedlight spectrum to a quaternary code information according to theembodiment of the third invention.

FIG. 16A is a perspective view which shows a method for writing down anidentification code according to the embodiments of the second, third,fourth, and fifth invention.

FIG. 16B is a perspective view which shows a method for writing down anidentification code according to the embodiments of the second, third,fourth, and fifth invention.

FIG. 16C is a perspective view which shows a method for writing down anidentification code according to the embodiments of the second, third,fourth and fifth invention.

FIG. 17A is a graphic representation which shows a method for convertinga reflected light spectrum to a binary code information according to theembodiment of the fourth invention.

FIG. 17B is a table which shows a method for converting a reflectedlight spectrum to a binary code information according to the embodimentof the fourth invention.

FIG. 18 shows a block diagram of a code reading device and itsperipheral devices according to the embodiment of the fifth invention.

FIG. 19 shows a method for converting a reflected light to a codeinformation according to the embodiment of the fifth invention.

FIG. 20 is a perspective view of an example of a code informationaccording to an embodiment of the sixth invention.

FIG. 21A is a graphic representative which shows a method for convertinga backscattering light intensity to a binary code information accordingto the embodiment of the sixth invention.

FIG. 21B is a representative which shows a method for converting abackscattering light intensity to a binary code information according tothe embodiment of the sixth invention.

FIG. 21C is a table which shows a method for converting a backscatteringlight intensity to a binary code information according to the embodimentof the sixth invention.

FIG. 22 is a block diagram of a code reading device and its peripheraldevices according to the embodiment of the seventh invention.

FIG. 23 is a perspective view of an example of an identification codeaccording to the embodiment of the seventh invention.

FIG. 24 is a table which shows a method for converting existences ofreflecting parts to a binary code information according to theembodiment of the seventh invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a structure of a control system of optical lines facility,which is applied to a method for identifying an optical line of thisinvention. A terminal 2 which switches the optical lines is placedbetween a local communication office 1 and a house of subscribers 3. Aplurality of optical lines of which the one end is connected to atransmission device 4 inside of the office 1 are gathered as an opticalfiber cable 9, and extend to the terminal 2. The other end of everyoptical line is connected to one end of a respective optical lineextending to the house of subscribers 3 through an optical connector 10.As a result, the transmission device 4 inside of the office 1 and everyhouse of subscribers 3 are substantially connected by one respectiveline.

In the optical connector 10, it can be freely operated by hand to switchconnections. Before the switching is conducted, first, a routeinformation of the optical lines is checked by an identifying methoddescribed thereinafter with a code reading device 5 placed inside of theoffice 1. Then, the route information is transmitted from a controldevice 6 to a local controller 11, and the information is given to anoperator in the field through a display device 12. The operator conductsthe requested connector switching based on the route information. Afterthe switching is done, the route information is read again by the codereading device 5, and the route information is confirmed at the office 1side. Then, this route information is displayed at the display device 12through the control device 6 and the local controller 11, and theoperator confirms the condition of the switching.

FIG. 2 is a block diagram of an inner structure of the code readingdevice 5 and its peripheral devices. The code reading device 5 comprisesa light emitting unit 20 and a light receiving unit 21, and they arecontrolled by a computer 22 and a timing control circuit 23 which formthe control unit 6.

The light emitting unit 20 contains a light source 24 for emitting alight having an appropriate spectrum range such as white ray, anacoustooptic element 25 for controlling an on/off of an irradiation oflight from the light source 24, and lenses 26, 27 placed respectively atan input and an output of the acoustooptic element 25. A light emittedfrom the light source 24 is inputted to one end of the optical fiber 40as a detecting light through the lens 26, the acoustooptic element 25and the lens 27. The optical fiber 40 is a branch optical line whichconnects the optical fibers 50 as optical lines to be measured and thecode reading device 5. The optical fiber 40 is connected to the opticallines 50 with a connecting means 38. The connecting means 38alternatively connects the optical fiber 40 to one of the optical lines50.

The light receiving unit 21 contains a Michelson interferometer 30, anA/D convertor circuit 36 for converting an output signal from theMichelson interferometer 30 to a digital value and providing it to thecomputer 22, and an acoustooptic element 31 for controlling an on/off ofan input light to the Michelson interferometer 30 based on a signal fromthe timing control circuit 23. The numerals 32, 33 denote lenses, andthe numeral 34 denotes an optical fiber. The Michelson interferometer 30contains a movable mirror 300, a fixed mirror 301, a beam splitter 302,a movable mirror moving device 303, a position-of-movable-mirror readingdevice 304, a light receiving element 305, and lenses 306, 307. A lightinputted to the Michelson interferometer 30 from the optical fiber 34 isdiverged by the beam splitter 302, and one is led to the fixed mirror301 and the other one is led to the movable mirror 300. The lightsreflected by the mirrors come back to the beam splitter 302, andinterfere each other. The interference light is inputted to the lightreceiving element 305 through the lens 307 and is converted to anelectrical signal. At this time, as the optical path length inside ofthe interferometer is varied by moving the movable mirror 300, aninterference waveform called an interferogram is obtained. This is aprinciple of operation of the Michelson interferometer 30. Using thisprinciple, relative positions of the plurality of reflecting parts whichform an identification code 39 are detected.

Every optical line 50 has unique identification codes 39 written in. Theidentification code 39 consists of the plurality of reflecting parts,and each optical line has a different combination of relative positionsof the reflecting parts. The reflecting parts forming the identificationcode 39 are notches on the optical line 50, which are discontinuouspoints of refractive indices. FIG. 3 shows an example of theidentification code 39. The identification code 39 contains 4 notches51-54, and the notches 52, 53, 54 are respectively at a distance of 3mm, 10 mm and 15 mm from the notch 51. Accordingly, if the detectinglight from the light emitting unit 20 is inputted to the optical line50, the reflected light arrived at the light receiving unit 21 from theidentification code 39 includes optical path differences produced on thebasis of distances between notch. The optical path differences aredetected by the Michelson interferometer 30, so that the relativepositions of the notches 51-54 can be detected.

The identification code 39 is applied to the optical lines between thelocal communication office 1 and the terminal 2, and to the opticallines between the terminal 2 and the houses of subscribers 3 as shown inFIG. 1. If there is a plurality of terminals between the office 1 andthe houses 3, the identification code is also applied to the opticallines between the terminals.

Next, a method for reading an identification code 39 will be explained.For instance, if the detecting light is inputted to the optical line 50applied the identification code including the four reflecting parts51-54 as shown in FIG. 3, the light receiving unit 21 collaborates withthe computer 22 to get an interferogram shown in FIG. 4A. This meansthat a main interference light intensity is obtained when the opticalpath difference is zero, and sub interference light intensities areobtained for all combination of two reflecting parts chosen from thereflecting parts 51-54. Concretely, the sub interference intensitiesappear at the optical path difference of 3 mm, 5 mm, 7 mm, 10 mm, 12 mm,and 15 mm.

FIG. 4B is a chart of an observational result corresponding to a codeinformation. The 15 bits code information "001010100101001" is obtainedfrom the observational result in FIG. 4A. The content of the codeinformation is set freely as selecting a number of the reflecting partsor positions of the reflecting parts.

In this embodiment, the optical line which connects the office 1 and thehouse of subscribers 3 consists of two divided optical lines connectedwith the terminal 2. Since the identification code is applied to everydivided optical line, they have to be distinguished and confirmed. Forthis reason, the acoustooptic element 31 is used. In other words, thepulsed detecting light is inputted to the optical line to be measured onthe basis of the control of the timing control circuit 23, and based onthe input timing of the detecting light, the reflected light from everyidentification code on the same optical line is periodically pick up bythe acoustooptic element 31. Therefore, the reflected lights from theidentification codes at different points on the same optical line isdistinguished. while the computer 22 distinguishes the reflected lightfrom every identification code, it obtains a data of the lightintensities of the reflected lights, and gets the interferogram of everyidentification code on the same optical line based on the input timingof the detecting light. Picking up the reflected light periodically canbe achieved with an optical gate (optical deflector) instead of theacoustooptic element 31.

Further, instead of writing the identification code directly to theoptical line, a branch optical line 101 in which the identification codeis written can be connected thereto with a fiber coupler 102 as shown inFIG. 5.

FIG. 6 is a block diagram of a device for an identifying methodaccording to another embodiment of the invention. The embodimentdescribed above is to detect a relative positions of reflecting partsbased on an interference of reflected lights. On the other hand, thisembodiment is to detect a relative positions of reflecting parts bymeasuring an arrival time difference between reflected lights. A lightemittig unit 20 contains a semiconductor laser 66 for outputting a pulselight having a short pulse-width, and a laser drive circuit 65. A lightreceiving unit 21 contains a light receiving element 61, an A/Dconvertor circuit 62 with memories, and an averaging circuit 63. Thenumerals 64 and 67 denote lenses respectively.

In this embodiment, a pulsed detecting light is inputted to the opticalline 50, and a time variation in the reflected light intensities ismeasured, so that the code information corresponding to the relativepositions of the reflecting parts can be read. FIG. 7 shows a graph ofan example of a measurement result according to this embodiment. Theordinate indicates a reflected light intensity and the abscissaindicates a time. This example is to measure the reflected lights fromthe identification code having four reflecting parts including thereference reflecting part (the nearest reflecting part to the detectinglight emitting side). The reflected light 71 from the referencereflecting part is arrived first, and the reflected lights 72, 73 and 74are arrived in order of a distance close to the reference reflectingpart. Assuming the reflecting parts except the reference reflecting partcan be set only at five points equally separated, the 5 bitsidentification code can be made by existence of the reflecting part atthe each point. In FIG. 7, the code information "01101" is indicated.

Next, an embodiment according to a second invention will be explained.FIG. 8 is a block diagram of an inner structure of a code reading device5 and its peripheral devices in case that this embodiment applies to acontrol system of optical lines facility shown in FIG. 1. A code readingdevice 5 contains a light emitting unit 1020 and a light receiving unit1021, and they are controlled by a computer 1022 and a timing controlcircuit 1023 which form a control circuit 6.

The light emitting unit 1020 contains a light source 1024 for emitting alight having an adequate spectrum range such as white ray, anacoustooptic element 1025 for controlling an on/off of a light outputtedfrom the light source 1024, and lenses 1026, 1027 placed respectively atan input and an output of the acoustooptic element 1025. The lightemitted from the light source 1024 is inputted to one end of an opticalfiber 40 as a detecting light through the lens 1026, the acoustoopticelement 1025, and the lens 1027. The optical fiber 40 is a branchoptical line which connects optical fibers 50 to be measured and thecode reading device 5. The optical fiber 40 is connected to the opticallines 50 with a connecting means 38. The connecting means 38alternatively connects the optical fiber 40 to one of a plurality of theoptical lines 50.

The light receiving unit 1021 contains a Fabry-Perot etalon 1032 as aninterference spectroscope, an etalon controller 1033 for controlling aspace between two plane boards for a resonance in the etalon 1032,lenses 1030, 1031 placed respectively at an input and an output of theetalon 1032, a light receiving element 1034 for converting a lightintensity of the output light from the etalon 1032 to an electricalsignal, a boxcar integrator 1035 for periodically picking up an outputsignal from the light receiving element 1034 based on a signal from atiming control circuit 1023, and an A/D convertor circuit 1036 forconverting an output of the boxcar integrator 1035 to a digital signal.The etalon 1032 inputs a light from an optical fiber 41 connected to anoptical fiber 40 with a fiber coupler 37 and analyzes spectra. At thistime, the etalon controller 1033 controls a space between resonanceplanes in the etalon 1032 based on an instruction from a computer 1022.As the computer 1022 obtains a data from the A/D convertor circuit 1036with controlling the etalon 1032, it analyzes a wavelength of thereflected light.

Each optical line 50 has unique identification codes 39 written in. Theidentification code consists of a plurality of reflecting parts. Theeach reflecting part reflect a light having a specific wavelength only.The optical line has a different combination of specific wavelengths ofthe reflecting parts each other. Every reflecting part forming theidentification code 39 is a striped pattern formed by varying therefractive index of the optical line 50 locally. As a spatial frequencyof a variation of the refractive indices is adequately set, everyreflecting part can obtain a unique wavelength of the reflected light.As shown in FIG. 9A, the reflecting part is the striped pattern wherethe refractive index is varied over a specific cycle. Let the cycle ofthe striped pattern 1100 (a distance between the refractive indexvarying points which adjoin each other) is d and a mean refractive indexof the optical line at the reflecting part is n, the wavelength λ of thereflected light is represented as λ=2nd. Accordingly, as d and n areadequately set, the desired wavelength of the reflected light can beobtained. The reflecting parts 1100 obtained in such a way are set atplural points (in FIG. 9B, five points) on the optical line 50 as shownin FIG. 9B, and as the wavelengths λ₁ -λ₅ of the reflected lights areset adequately, the identification code can be formed. The refractiveindex can be varied permanently as a UV ray (Ultra Violet Ray) is partlyirradiated to the optical line 50. By using this, the reflecting partwhich reflects a specific wavelength only can be formed.

The identification code 39 is applied to the optical lines between theoffice 1 and the terminal 2, and to the optical lines between theterminal 2 and the houses of subscribers 3 as shown in FIG. 1. If thereis a plurality of terminals between the office 1 and the houses ofsubscribers 3, the identification code is also applied to the opticallines between the terminals.

Next, a method for reading an identification code 39 in this embodimentwill be explained. For instance, by using five wavelengths λ1-λ5, abinary number is coded. This means that existence of a reflected lightin the five wavelengths are corresponded to "1" or "0". FIG. 10A is agraph of an example of wavelength characteristics of the reflectedlights when the detecting light from the light emitting unit 1020 isgiven to the optical line 50. The graph shows a wavelength on theabscissa and a light intensity on the ordinate. In this example, thereflected lights at wavelengths of λ1, λ3 and λ5 can be observed, and onthe other hand, the reflected lights at wavelength of λ2 and λ4 cannotbe observed. FIG. 10B is a chart of an observational result correspondedto the code information. A five bits code information "10101" isobtained from the result in FIG. 10A.

In this embodiment, the optical line which connects the office 1 and thehouse of subscribers 3 consists of two divided optical lines connectedwith the terminal 2. Since the identification code is applied to everydivided optical line, they have to be distinguished and confirmed. Forthis reason, the boxcar integrator 1035 is used. In other words, thepulsed detecting light is inputted to the optical line to be measuredwhile the input timing is controlled by the timing control circuit 1023,and the reflected light from each identification code is periodicallypicked up based on the input timing of the detecting light. Therefore,the reflected lights from identification codes whose locations aredifferent from each other on the same optical line can be distinguished.As the computer 1022 distinguishes the reflected light from eachidentification code, it obtains a data of the reflected lightintensities in correspondence with the wavelength, so that the computergets the interferogram of each identification code. The distinction ofreflected light can be achieved with an optical gate (optical deflector)instead of the boxcar integrator 1035.

Instead of writing the identification code directly in the optical line,a branch optical line 1101 in which the identification code 1100 iswritten can be connected thereto with a fiber coupler 1102 as shown inFIG. 11.

In the embodiment described above, the white-light source 1024 is usedas the light source, and the Fabry-Perot etalon 1032 is used as thespectroscope in the light receiving unit 1021. Instead of them, when alight source 1109 which is a wavelength switching type is used in thelight receiving unit 1021 as shown in FIG. 12, the spectroscope in thereceiving unit 1021 can be omitted. The light source 1109 incorporates asemiconductor laser array 1110, a prism 1113, and a condenser lens 1027.The semiconductor laser array 1110 includes a plurality of thesemiconductor lasers 1111 for emitting light of different wavelengths,and a lens 1112 which is placed at every semiconductor laser 1111. Acontrol circuit 1114 controls a drive of the semiconductor laser 1111and a movement of the prism 1113. Then, the light source 1109 canselectively outputs a detecting light having a required wavelength. Thewavelength of the reflected light at every reflecting part is selectedamong the wavelengths emitted from the semiconductor lasers 1111.Accordingly, if the wavelength of the detecting light is subsequentlyswitched and the existence of the reflected light at every wavelength isdetected when the identification is conduced, similarly to theembodiment described above, the wavelength of the reflected light forevery reflecting part can be obtained. In this embodiment, in order toperiodically pick up the reflected light, the boxcar integrator 1035 isoperated based on the timing signal from the control circuit 1114. Butit is also possible that a light receiving element is placed at unusedend of the optical fiber 41 to detect an input timing of the detectinglight, and this detecting light is used as an operational timing signalfor the boxcar integrator 1035.

FIG. 13 is a perspective view of a structure of another example of areflecting part used as an identification code 39. In this example, anoptical filter is used as a reflecting part which reflects a specificwavelength only. A method for forming the identification code will bebriefly explained. Two V-shaped notches 1201, 1202 are formed on asilicon board 1200, and core fibers 1204 and 1205 of a double core tapefiber 1203 which are optical lines are buried in respectively. Then, asilicon lid is put over and is hardened with a resin 1207 to fix theoptical fibers 1204 and 1205. Next, as a notch 1208 is formed on thesilicon board 1200 over the silicon lid 1206, the optical fibers 1204and 1205 are cut. Then, a desired monochromatic reflecting opticalfilter 1210 is inserted in the notch 1208, so that the reflecting partwhich reflects a specific wavelength only is formed on the optical line.The optical filter 1210 is formed by a dielectric multiple layered filmetc. Using the method with this optical filter, in case that the opticalline is either a double core tape fiber like in this example ormulticore tape fiber, it is possible to apply the same identificationcode to every optical fiber at the same time.

FIG. 14 is a perspective view of an example of an optical filter placedin a connector. Usually, an optical line is formed as a plurality ofdivided optical fibers is connected by connectors. In this example, asthe optical filter which comprises an identification code is placed onone side of a connector, an installation of the optical filter becomeseasy. The connector includes a male connector 1220 having a guide pin1221, and a female connector 1223 having receiving holes for the guidepin 1221. Each connector 1220, 1223 has a structure that two siliconchips 1224, 1225 are piled and hardened with an epoxy resin 1226. Anumber of V-shaped notches equal to or larger than the number of opticalfibers forming a tape fiber 1227 are placed on the silicon chip 1224,and each optical fiber is fixed in the V-shaped notch. As the guide pins1221 are inserted to the receiving holes 1222, the optical fibers on theside of the male connector 1220 and the optical fibers on the side ofthe female connector 1223 are coupled one by one. Before the coupling, amonochromatic reflecting optical filter 1230 is inserted between them,so that the identification code can be formed on the optical line. Inthis example, the optical filter is made separately from the connectors1220, 1223. But it is possible to form a dielectric multiple layeredfilm on one side of the female connector 1223 by vapor-deposition.

Next, an embodiment corresponding to a third invention will beexplained. This embodiment is similar to the second invention alreadyexplained with FIG. 8-FIG. 14. A point of difference is to use not onlya wavelength of a reflected light but also a reflected light intensityas an identification code. This embodiment is also applied to a controlsystem of optical lines facility as shown in FIG. 1. An inner structureof a code reading device and its peripheral devices are shown in FIG. 8.

An identification code 39 consists of a plurality of reflecting parts.The each reflecting part reflect a light having a specific wavelengthonly. Each optical line has a different combination of specificwavelengths and reflectance. Using the reflectance also as anidentification code is different from the second invention. Everyreflecting part forming the identification code 39 contains stripedpattern where refractive indices are varied locally on the optical line50. As a spatial frequency of a variation of the refractive indices or avalue of the refractive index is adequately set, every reflecting partcan obtain a unique wavelength of the reflected light and thereflectance. As shown in FIG. 9A, the reflecting part contains stripedpattern where the refractive indices are varied over a specific cycle.Let a cycle of the striped pattern 1100 (i.e. a distance between therefractive index varying points which adjoin each other) is d and a meanrefractive index of the optical line at the reflecting part is n, thewavelength λ of the reflected light is represented as λ=2nd.Accordingly, as d and n are adequately set, the desired wavelength ofthe reflected light can be obtained. The desired reflectance can beobtained by conducting the number of stripes and the difference of therefractive indices at striped pattern. The reflecting part 1100 obtainedin such a way is set at plural parts (In FIG. 9B, five parts) on theoptical line 50 as shown in FIG. 9B, and as the wavelengths λ₁ -λ₅ andthe reflectances of the reflected lights are adequately set, theidentification code can be formed. The refractive index can be varied asa UV ray (Ultra Violet Ray) is partly irradiated to the optical line. Byusing this, the reflecting part which reflects a light with a specificwavelength and reflectance only can be formed.

The identification code 39 is applied to the optical lines between theoffice 1 and the terminal 2, and to the optical lines between theterminal 2 and the houses of subscribers 3 as shown in FIG. 1. If thereis a plurality of terminals between the office 1 and the houses ofsubscribers 3, the identification code is also applied to the opticallines between the terminals.

Next, a method for reading an identification code in this embodimentwill be explained. For instance, using six wavelengths λ₀ -λ₅, a 4notation number is coded. This means that if λ₀ is a reflectedwavelength at a reference reflecting part, and based on the reflectedlight intensity at the reference reflecting part, the other reflectedlights with wavelengths λ₁ -λ₅ are corresponded to one of "0-3". FIG.15A is a graph of an example of wavelength characteristics of thereflected lights when the detecting light from a light emitting unit 20is given to the optical line 50. The graph shows a wavelength on theabscissa and a light intensity on the ordinate. In this example, thereflected lights at wavelengths λ₁ -λ₅ are respectively corresponding tothe reflected light intensities "a,0,3a,0,2a". FIG. 15B is a chart of anobservational result corresponded to a code information. The codeinformation "10302" is obtained from the result in FIG. 15B.

In this embodiment, similar to the embodiment according to the secondinvention, the identification code on every divided optical line can bedistinguished by the boxcar integrator 1035.

The identification code can be written in a branch optical line as shownin FIG. 11.

Further, it is possible to apply the embodiments already described withFIG. 12-FIG. 14.

Next, an embodiment according to a fourth invention is also applied to acontrol system of optical lines facility as shown in FIG. 1. An innerstructure of a code reading device and its peripheral devices are shownin FIG. 8. In this embodiment, an identification code 39 includes areflecting part where the reflectance depend on wavelengths. Thereflecting part contains striped pattern where the refractive indicesare locally varied. As a spatial frequency of a variation of therefractive indices or a value of a refractive index is adequately set,the reflected light spectrum can be obtained. The reflected lightspectrum is a content of the identification code 39. The identificationcode 39 is applied to the optical line between the office 1 and theterminal 2, and to the optical line between the terminal 2 and thehouses of subscribers 3 as shown in FIG. 1. If there is a plurality ofterminals between the office 1 and the houses of subscribers 3, theidentification code is also applied to the optical lines betweenterminals.

FIG. 16A-FIG. 16C show a method for writing reflecting parts which forman identification code 39. Every figure shows that as a UV ray (UltraViolet Ray) is locally irradiated to the optical line 50 to vary arefractive index of the irradiated part, the reflecting part having adesired reflected light spectrum is formed. FIG. 16A shows a method forrecording with a hologram. The UV ray 2062 is irradiated to the hologram2061, and the diffracted lights by a hologram pattern recorded on thehologram 2061 are projected to the optical line 50. The refractive indexis locally varied corresponding to a pattern formed by the diffractedlights, so that the reflecting part 2064 containing stripes of variedrefractive index is formed on the optical line 50. The pattern made bythe diffracted lights is freely set by changing a hologram pattern. FIG.16B shows a method for forming a reflecting part 2074 having the stripedpattern with the refractive index varied by condensing the UV ray 2072with a lens 2073, and projecting a mask pattern 2071 having specificintervals and transmissivity of stripes to the optical line 50. FIG. 16Cshows another method for forming a reflecting part having the stripedpattern with the refractive index varied. This method comprises acontrol process of a UV ray intensity by forming a slit image with theUV ray 2083 on an optical line 50 using a slit 2081 and a lens 2082 anda control process of a movement of the slit image. While the UV rayintensity is adequately varied, the slit image is moved along theoptical line 50 with a control of its speed to form the reflecting part.These method for writing the identification code can be applied to theembodiments according to the second and third invention described aboveand to an embodiment according to a fifth invention describedthereinafter.

Next, a method for reading an identification code 39 of this embodimentwill be explained. FIG. 17A is a graph of an example of a reflectedlight spectrum at an identification code 39 when the detecting lightfrom a light emitted unit 1020 is given to the optical line 50. In thisgraph, the abscissa indicates a wavelength and the ordinate indicates alight intensity. A threshold level 2092 is adequately set to thereflected light spectra 2091, and a binary code is applied to eachwavelength based on whether the light intensity at each of wavelengthsλ₁ -λ_(n) is larger or smaller than the threshold level 2092. FIG. 17Bshows a corresponding chart between the wavelengths and binary cords. Inthe chart, when the light intensity is larger than the threshold level2092, "1" is given, and when the light intensity is smaller than thethreshold level 2092, "0" is given. In such a way, the reflected lightspectra can be easily coded to a binary digit. It is possible that themethod for setting a threshold level 2092 is to set a light intensity ata specific wavelength of a reflected light as a threshold level 2092other than the method for setting a threshold level in advance.

In this embodiment, similar to the embodiment according to the secondinvention, the identification code on every divided optical line can beperiodically picked up by the boxcar integrator 1035.

The identification code can be written to a branch optical line as shownin FIG. 11.

Further, it is possible to apply the embodiments already described withFIG. 12-FIG. 14.

Next, an embodiment according to a fifth invention will be explained.FIG. 18 is a block diagram of an inner structure of a code readingdevice 5 and its peripheral devices in case that this embodiment appliesto a control system of optical lines facility shown in FIG. 1.

The light emitting unit 3020 contains a light source 3109 and its drivecontrol circuit 3114. The light source 3109 incorporates a semiconductorlaser array 3110, a prism 3113, and a condenser lens 3027. Thesemiconductor laser array 3110 contains a plurality of semiconductorlasers 3111 which emit lights of different wavelengths, and a lens 3112which is placed at every semiconductor laser 3111. The drive controlcircuit 3114 selectively controls a drive of the semiconductor laser3111 and a movement of the prism 3113, so that the light source 3109 canselectively output a detecting light having a required wavelength. Anoptical fiber 40 is a branch optical line which connects optical fibers50 to be measured and a code reading device 5, and is connected to theoptical fibers 50 to be measured with a connecting means 38. Theconnecting means 38 selectively connects the optical fiber 40 to one ofthe optical lines 50 to be measured.

A light receiving unit 3021 contains a light receiving element 3034 forconverting an inputted light to an electrical signal, and an A/Dconvertor circuit 3035 with memories for converting a signal from thelight receiving element 3034 to a digital value, and an averagingcircuit 3036 for averaging the digital value from the A/D convertorcircuit 3035. An optical fiber 41 is connected to the optical fiber 40with an optical fiber coupler 37, and one end is led to the lightreceiving unit 3021. The A/D convertor circuit 3035 stores a timevariation in signals from the light receiving element 3034 based on theemitting timing of the detecting light from the drive control circuit3114 and converts an analog data to a digital data in an appropriateinterval. Accordingly, a period from time when the light emitting unit3020 emits the detecting light to time when the reflected light comesback can be detected.

Since the reading unit 5 is constructed in this way, a computer 3022 canidentify a specific wavelength of every reflecting part which forms anidentification code 39 and a relative position thereof, using acombination of the wavelength of a detecting light and the time when thereflected light at the identification code 39 arrives.

Each optical line 50 has unique identification codes 39 written in. Theidentification code 39 consists of a plurality of reflecting parts. Eachreflecting part reflects a light having a specific wavelength only. Eachoptical line has a different combination of specific wavelengths andrelative positions of reflecting parts. Every reflecting part formingthe identification code 39 contains striped pattern where refractiveindices are varied locally on the optical line 50. As a spatialfrequency of a variation of the refractive indices etc. are adequatelyset, every reflecting part can obtain a unique wavelength of thereflected light. As shown in FIG. 9A, the reflecting part containsstriped pattern where the refractive indices are varied over a specificcycle. Let a cycle of the striped pattern 1100 (i.e. a distance betweenrefractive index varying points which adjoin each other) is d and a meanrefractive index of the optical line at the reflecting part is n, thewavelength λ of the reflected light is represented as λ=2nd.Accordingly, d and n are adequately set, so that the desired wavelengthof the reflected light can be obtained. The reflecting part 1100obtained in such a way is set at plural parts (In FIG. 9B, 5 parts) onthe optical line 50 as shown in FIG. 9B, and as the wavelengths λ₁ -λ₅of the reflected lights and relative positions of the reflecting pantsare set adequately, the identification code can be formed. Therefractive index can be varied as a UV ray (Ultra Violet Ray) is locallyirradiated to the optical line 50. By using this, the reflecting partwhich reflects a specific wavelength only is formed.

The identification code 39 is applied to the optical lines between theoffice 1 and the terminal 2, and to the optical lines between theterminal 2 and the houses of subscribers 3 as shown in FIG. 1. If thereis a plurality of terminals between the office 1 and the houses ofsubscribers 3, the identification code is also applied to the opticallines between the terminals.

Next, a method for reading an identification code 39 of this embodimentwill be explained. For instance, n notation number is coded with n kindsof wavelengths λ₁ -λ_(n) as wavelengths of reflected lights. This meansthat numbers 1 to n are assigned to every wavelength. Then, a reflectingpart having a wavelength characteristic selected from these wavelengthsis applied to m points of the optical line 50. Accordingly, the nnotation number of m figure can be coded with the specific wavelengthsof the reflecting parts and their relative positions. Since the codereading device 5 can detect the wavelength of the detecting light andthe arrival time of the reflected light, the code can be read. FIG. 19shows a combination chart of wavelengths and the relative positions ofthe reflecting parts. This chart indicates that the wavelength λ₂ isformed first, λ₁ is a second, λ₃ is a third and so on, and as readingthis and converting it to a code, "213 . . . " is made

In the embodiment above, the A/D convertor circuit 3035 is driven basedon the timing signal from the drive control circuit 3114, but it ispossible that with the light receiving element placed at unused end ofthe optical fiber 41, the input timing of the detecting light isdetected, and this detected signal is used as an operational timingsignal for the A/D convertor circuit 3035.

The identification code can be written in a branch optical line as shownin FIG. 11.

Further, it is possible to apply the embodiments already explained withFIG. 13-FIG. 14.

Next, an embodiment according to a sixth invention will be explained. Inthis embodiment, a code reading device shown in FIG. 6 is applied to thesystem shown in FIG. 1.

Each optical line 50 has unique identification codes 39 written in. Theidentification code 39 consists of a plurality of bending loss parts. Acombination of relative positions of the bending loss parts is changedfor each optical line. Every bending loss part forming theidentification code 39 is a bending part on the optical line 50, and aconcrete example of a jig is shown in FIG. 20. The jig 4080 consists areceiving member 4081 with V-shaped notches and a weight member 4082. Inthe receiving member 4081, concavities are formed at the V-shapednotches corresponding to a required identification code. Here, theconcavities 4083-4086 are formed in the first, third, fourth, andseventh notch. On the weight member, projections 4087-4090 are formed atthe position corresponding to the concavities on the receiving member4081. The optical line 50 is meandered and inserted in the V-shapednotches on the receiving member 4081 and weighted over with the weightmember 4082, so that the bending loss parts are formed at the first,third, fourth, and seventh V-shaped notch. At the code reading device 5,a pulsed detecting light is inputted to the optical line 50, and a timevariation in backscattering light intensities is measured, so that acode information corresponding to a relative position of each bendingloss part is read.

The identification code 39 is applied to the optical lines between theoffice 1 and the terminal 2, and to the optical lines between theterminal 2 and the houses of subscribers 3 as shown in FIG. 1. If thereis a plurality of terminals between the office 1 and the houses ofsubscribers 3, the identification code is also applied to the opticallines between the terminals.

Next, a method for reading an identification code 39 in this embodimentwill be explained. When a detecting light is inputted to the opticalline 50 having the identification code formed with the four bending lossparts as shown in FIG. 20. The light receiving unit 21 collaborates withthe computer 22 to obtain a characteristic of a time variation in thebackscattering light intensities as shown in FIG. 21A. This means thatat the each bending loss part, the backscattering light intensityrapidly decreases based on the irradiation loss. FIG. 21B shows a resultof the differentiated characteristics. In this graph, peaks 4095, 4096,4097 and 4098 are corresponding to the first, third, fourth and seventhbending loss part formed in the V-shaped notches. Assuming that thefirst bending loss part is a reference bending loss part and anexistence of the bending loss part in 7 V-shaped notches except thenotch for the first bending loss part is coded, the characteristicsshown in FIG. 21B can be replaced with a seven bits code shown in FIG.21C. The content of the code information is set freely as selecting anumber of the bending loss parts or positions of the bending loss parts.

In this embodiment, the optical line which connects the office 1 and thehouses 3 of subscribers consists of two divided optical lines connectedwith the terminal 2. Since the identification code is applied to everydivided optical line, they have to be distinguished and confirmed. Inorder to do that, as an operation of the A/D convertor circuit 62 withmemories is periodically controlled by timing control circuit 23, avariation of the light intensities is periodically picked up based onthe input timing of the detecting light. Therefore, the variation of thelight intensities at different points of the identification code on thesame optical line can be distinguished. Picking up the backscatteringlight can be achieved with an optical gate (optical deflector). As shownin FIG. 11, the identification code can be written in a branch opticalline.

Next, an embodiment according to a seventh invention will be explained.In this embodiment, a code reading device shown in FIG. 22 is applied tothe system shown in FIG. 1. In this embodiment, optical lines betweenthe office 1 and terminal 2 are gathered to be a multicore optical line,and further the multicore optical lines are gathered to be an opticalfiber 9. The identification of the optical line described thereinafteris related to an identification of a multicore optical line. In thiscase, each mono-optical line inside of the multicore optical line iscalled a core optical fiber.

FIG. 22 shows a block diagram of an inner structure of a code readingdevice 5 and its peripheral devices. A code reading device 5 consists ofa light emitting unit 5020 and a light receiving unit 5021, and they arecontrolled by a computer 5022 and a timing control circuit 5023 whichform a control circuit 6.

The light emitting unit 5020 contains a light source 5024 for emitting alight having an adequate spectrum range such as white ray, anacoustooptic element 5025 for controlling an on/off of a light outputtedfrom the light source 5024, and lenses 5026, 5027 placed respectively atan input and an output of the acoustooptic element 5025. The lightemitted from the light source 5024 is inputted to one end of an opticalfiber 40 as a detecting light through the lens 5026, the acoustoopticelement 5025, and the lens. 5027. The optical fiber 40 is a branchoptical line which connects one of the multicore optical lines 50 to bemeasured and the code reading device 5. The optical fiber 40 isconnected to the multicore optical line 50 with a connecting means 38.In this embodiment the optical fiber 40 is also a multicore opticalfiber having a number of cores equal to the number of core fibers ofoptical line 50. The connecting means 38 alternatively connects themulticore optical fiber 40 to one of a plurality of the multicoreoptical lines 50 to be measured.

A light receiving unit 5021 contains a number of light receivingelements 5031 equal to the number of core fibers of the multicoreoptical line for converting an inputted light to an electrical signal,and an A/D convertor circuit 3035 for converting a signal from the lightreceiving element 5031 to a digital value and transmitting the digitalvalue to a computer 5022, and a lens 5033 placed in front of every lightreceiving element 5031. The light receiving element 5031 receives alight from an optical fiber 41 connected to an optical fiber 40 with afiber coupler 37 and converts the light to an electrical signal. Theoptical fiber 41 is also a multicore optical fiber having a number ofoptical core fibers equal to the number of core fibers of a multicoreoptical line 50 that is the number of core fibers of the optical fiber40. Each core optical fiber of the optical fiber 41 is led to the lightreceiving element 5031. Accordingly, the existence of the reflectedlight at every core optical fiber can be detected. The light receivingelements 5031 are controlled by the timing control circuit 5023, and thelight receiving element is operated subsequently from the left hand ofthe figure, so that the reflected light at the each core optical fiberis subsequently provided to the A/D convertor circuit 5032.

Unique identification codes 39 are written in each optical line 50. Theidentification code is formed by placing reflecting parts selectively oncore optical fibers of the multicore optical line and changing acombination of the existence of the reflecting part at the core opticalfibers for every multicore optical line. FIG. 23 shows an example of theidentification code at the multicore tape optical line. Each coreoptical fiber 5061 of the multicore tape optical line 5060 is exposed tobe a part on which the identification code will be made. The reflectingpart 5063 is selectively made at this part. The reflecting parts 5063can be formed as the refractive indices are varied by irradiating to thecore optical lines 5061 with a UV ray (Ultra Violet Ray). The reflectingparts 5063 can be also formed by cutting the core optical fibers andinserting an optical filter into the cutting part. In the FIG. 23,identification code part 5063 remains being exposed for easyexplanation. This part will be fixed by a board like a silicon chip tomaintain a mechanical strength in practice.

Next, a method for reading an identification code 39 will be explained.Here, a multicore optical line is 8-core tape optical fiber. As thedetecting light is inputted to the all (eight) core optical fibers ofthe tape optical fiber to be read, the receiving unit 5021 receives onlya reflected light from the core optical fiber having a reflected part.These reflected light is detected at the light receiving element 5031corresponding to the core optical fiber one by one, and the signal isinputted to the computer 5022 through the A/D convertor circuit 5032.FIG. 24 shows a chart of a detection result. All core optical fibers arenumbered 1-8. By the existence of the reflecting part at the eachnumbered core optical fiber, the detection of the reflected light ismade. When the reflected light is detected, a code "1" is given and whenthe reflected light is not detected, a code "0" is given, so that the 8bits code information is obtained from the detecting result.

Further, as shown in FIG. 11, the identification code can be written toa branch optical line.

INDUSTRIAL APPLICABILITY

In accordance with the identifying method of the present invention,

1 each optical line has a different combination of positions of aplurality of reflecting parts forming an identification code, and therelative positions are detected,

2 each optical line has a different combination of reflectivewavelengths of a plurality of reflecting parts forming an identificationcode, and the wavelengths of the reflected lights are measured,

3 each optical line has a different combination of reflectivewavelengths and reflectances of a plurality of reflecting parts formingan identification code, and the wavelengths and light intensities of thereflected lights are measured,

4 each optical line has a different reflective wavelength characteristicof reflecting parts forming an identification code, and spectra of thereflected lights are measured,

5 each optical line has a different combination of reflectivewavelengths and relative positions of a plurality of reflecting partsforming an identification code, and the wavelengths and the relativepositions of the reflecting parts are measured based on reflected lightsfrom the identification code,

6 each optical line has a different combination of relative positions ofa plurality of bending loss parts, and the relative positions aredetected,

so that the optical line can be easily and accurately identified.Accordingly, the invention is effective to the confirmation ofconnections in case that a switching is operated at the terminal.

In case that the optical line is a multicore type, reflecting parts canbe selectively applied to core optical lines to form an identificationcode. For all core optical lines, as an existence of a reflected lightis measured, the multicore optical line can be easily and accuratelyidentified.

What is claimed is:
 1. An optical wave guide having at least onediffraction grating area, said diffraction grating area being formed byirradiating light on a mask pattern to magnify a light pattern passingthrough said mask-pattern with an optical system, thereby projecting amagnified light pattern on said optical wave guide, wherein a refractiveindex of said diffraction grating area corresponds to an intensity ofsaid light pattern passing through said mask pattern wherein a pluralityof diffraction grating areas are provided on the optical wave guide andare arranged along a longitudinal direction, the optical wave guidebeing identifiable according to at least one characteristic of lightreflected by said diffraction grating areas in response to lightsupplied to an end of the optical wave guide.
 2. An optical wave guidehaving at least one diffraction grating area, said diffraction gratingarea being formed by irradiating light through a hologram pattern so asto project a diffractive light caused by said hologram pattern on theoptical wave guide, a refractive index of said diffraction grating areacorresponding to an intensity of said diffractive light.
 3. An opticalwave guide according to claim 2, wherein a plurality of diffractiongrating areas are provided on the optical wave guide and are arrangedalong a longitudinal direction of the optical wave guide, whereby theoptical wave guide is identifiable according to at least onecharacteristic of light reflected by said plurality of diffractiongrating areas in response to light supplied to an end of the opticalwave guide.
 4. A method of fabricating a diffraction grating on anoptical wave guide, comprising the steps of:preparing an optical waveguide; irradiating a light on said optical wave guide through a hologrampattern so as to project diffractive light caused by said hologrampattern on said optical wave guide, thereby forming areas of whichrefractive index corresponds to an intensity of said refractive light tobe projected on said optical wave guide.
 5. A method according to claim4, wherein said light irradiated on said hologram pattern is anultraviolet ray.
 6. A method according to claim 4, wherein said opticalwave guide comprises an optical fiber.
 7. A method of fabricating adiffraction grating on a diffraction grating area of an optical waveguide, comprising the steps of:preparing an optical wave guide; andirradiating light on a mask pattern, including magnifying a lightpattern passing through said mask pattern using an optical system,thereby projecting said magnified light pattern on said optical waveguide, wherein a refractive index of the area corresponds to anintensity of said light pattern passing through said mask patternwherein said optical system used in said magnifying step comprises alens.
 8. A method according to claim 7, wherein said light irradiated onsaid mask pattern is ultraviolet.
 9. A method according to claim 7,wherein said optical wave guide comprises an optical fiber.